During the semester we have a high energy seminar and a lunch seminar. In addition to these two seminars we participate in a joint theoretical high energy theory seminar in Newe Shalom. The joint seminar takes place on Tuesdays from 10:30 until 13:30 and includes two talks and lunch. This seminar is attended by the high energy groups of all the Israeli institutions and usually attracts a crowd of roughly twenty participants.
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Title: Krylov complexity in quantum field theory and beyond
Abstract: Krylov complexity, and dynamics in Krylov space more generally, have emerged recently as interesting probes of quantum dynamics. They were proposed as probes of quantum chaotic dynamics, relating the latter to growth of OTOC. We discuss Krylov dynamics in case of quantum field theory, and first notice that in the conformal case Krylov complexity behaves universality with no regard to integrability or chaos of the underlying theory. We then discuss turning on mass, placing the theory on a space of finite size and/or introducing a UV cutoff. We notice that each of these deformations is reflected in Lanczos coefficients and in the behavior of Krylov complexity. We conclude with a conjecture strengthening the Maldacena-Stanford-Shenker bound on OTOC, outlining the role of UV cutoff in the context of “universal operator growth hypothesis” and argue behavior of Krylov complexity is qualitatively different from computational and holographic complexities.
Title: A simple model, extracted using holography, of a domain wall between a confining and a de-confining phases and its velocity.
Abstract: In the context of theories with a first order phase transition, we propose a general covariant description of coexisting phases separated by domain walls using an additional order parameter-like degree of freedom. In the case of a holographic dual to a confining and a de-confing phases, the re- sulting model extends hydrodynamics and has a simple formulation in terms of an action and a corresponding energy-momentum tensor. The proposed description leads to simple analytic profiles of domain walls, including the surface tension density, which agree nicely with holographic numerical solu- tions. We show that for such systems, the domain wall or bubble velocity can be expressed in a simple way in terms of a perfect fluid hydrodynamic formula, and thus in terms of the equation of state. We test the predictions for various holographic domain walls.
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Title: Mixed anomalies and generalized symmetries from 3d superconformal indices
Abstract: Generalized symmetries and their mixed anomalies have proved to be useful in providing non-trivial constraints on the dynamics of QFTs. A natural question is whether these are related in any way to supersymmetric partition functions or indices, which have also been used extensively to study SQFTs. In this talk, we address this question in the context of 3d $mathcal{N} geq ≥3$ gauge theories using the superconformal index. In particular, using the index we are able to detect mixed anomalies involving discrete 0-form symmetries, and possibly a 1-form symmetry. Gauging appropriate symmetries involved in such mixed anomalies, we obtain various interesting theories with two-group structures or non-invertible symmetries.
Title: Entanglement, Chaos and Quantum Computation
Abstract: We consider information spreading measures in randomly initialized variational quantum circuits and introduce entanglement diagnostics for efficient computation. We study the correlation between quantum chaos diagnostics, the circuit expressibility and the optimization of the control parameters.
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Title: Thermalization and Chaos in 1+1d QFTs
Abstract: Nonintegrable QFTs are expected to thermalize and exhibit emergence of hydrodynamics and chaos. In weakly coupled QFTs, kinetic theory captures local thermalization; such a versatile tool is absent away from the perturbative regime. I will present analytical and numerical results using nonperturbative methods to study thermalization at strong coupling. I will show how requiring causality in the thermal state leads to strong analytic constraints on the thermodynamics and out-of-equilibrium properties of any relativistic 1+1d QFT. I will then discuss Lightcone Conformal Truncation (LCT) as a powerful numerical tool to study thermalization of QFTs. Applied to phi^4 theory in 1+1d, LCT reveals eigenstate thermalization and onset of random matrix universality at any nonzero coupling. Finally, I will discuss prospects for observing the emergence of hydrodynamics in QFTs using Hamiltonian truncation.